Scientists are concerned about the pesticide glyphosate, but not the approval authority. How did that happen?

The pesticide watchdog can rest for a while. While emotions have risen in The Hague and Brussels in recent months about the world’s most popular pesticide, glyphosate, the work was just over for the Dutch Board for the Authorization of Plant Protection Products and Biocides (Ctgb). This Ctgb had collaborated for years on the European advisory report on glyphosate, published before a European vote on the drug. Ultimately, ‘knowledge gaps’ were noted, but no ‘critical concerns’.

The exceptional size of the report illustrates how controversial the pesticide has become. Professors and environmental groups expressed their concerns increasingly loudly and the House of Representatives twice called on outgoing Minister Adema (Agriculture, Nature and Food Quality, Christian Union) to vote against approval of the drug in Brussels. Adema showed himself to be loyal to the Ctgb advice and ignored both motions. Votes in Brussels ended in deadlock. The European Commission then decided to stick with its own proposal: farmers in Europe will be allowed to continue spraying their plots with glyphosate for the next ten years.

Now that the pesticide has been approved in Europe, it is the Ctgb’s turn again. The Netherlands will have to judge whether all products in which the substance is processed – the best known are RoundUp and Touchdown – can be used safely. It will direct the industry to resolve all questions that remained after the European admission advice.

Ctgb director Ingrid Becks and toxicologist Rixta Hempenius, who was directly involved in the European advice, explain the charged dossier.

Is glyphosate safe?

Becks: “We have had a lot of internal discussions lately: what is safe? In fact, society and politics have determined that for us. The law stipulates which studies must be submitted to us and how we must assess them. We are an executive organization. If an active substance such as glyphosate complies with the rules, there are no ‘unacceptable risks’ for humans, the environment and the animals living in it. Our conclusion is that you can use glyphosate safely if you do so according to the regulations.”

Water is also poisonous to a human if you ingest eight liters

But is it impossible that people experience effects?

Hempenius: “Our assessments always concern exposure and the dosage at which a substance is harmful. A simple example: water is also poisonous to a human if you ingest eight liters. The dosage makes the poison.

“We work with many results from animal studies. It is important that we see effects, so that you can establish a safe standard. With a good study design, you test higher and lower doses in the short and long term, and we look at different effects: on development, organs, reproduction, and cancer development, among other things. At the lowest dose you should no longer see any effects at all, and we then apply a safety margin of a factor of one hundred, at which you should certainly see no effects in humans.”

Becks: “We speak of ‘no unacceptable risk’, because apart from the required studies, there are also things we cannot know. Politics or society might have an opinion about that, but you also have to look at what is proportional. Society is never completely without risk.”

Criticism of the pesticide has increased in recent months. In November, an urgent letter from 159 scientists was published: “Take independent science seriously when deciding on glyphosate.” The use has been linked to cancer, damage to the microbiome – the microorganisms – in the intestines, biodiversity and neurodegenerative diseases such as Parkinson’s. Neurologist Bas Bloem in particular warned in the media, including in NRC. And after the decision to allow glyphosate in Europe, activist group Pesticide Action Network announced a lawsuit.

What was it like to assess such a charged file?

Becks: “I understand very well that people are concerned. Pesticides are substances that we introduce into our environment with a purpose: to kill an insect, weed or fungus. It is a requirement that we look at this very strictly and critically. We feel that important social responsibility. We have good experts who know what they are talking about and who are very committed.

We realize that this substance is under a magnifying glass

“On the other hand, we realize that this chemical is under a magnifying glass. And that is reflected in a very polarized discussion. As a scientific organization, it is difficult to be drawn into the social debate. It had no influence on our work, but it did become difficult because trust in our institute came into question. That really does an injustice to the people who work here.”

Many scientists also express their concerns, for example in the urgent letter to the minister. How do you view those criticisms?

Hempenius: “There are several discussions surrounding glyphosate, for example: can it cause Parkinson’s? Or is there an effect on the microbiome? What about biodiversity? You see that these are issues for which good methodology is lacking in our admission system, not just for glyphosate.”

Becks: “We have regular contact with scientists who express concerns, including Bas Bloem. This has led us to jointly say that there is no good methodology available to test whether certain substances cause Parkinson’s. We have written a letter to the European approval authority EFSA. Minister Adema has supported this and put it on the agenda in Europe.”

Bas Bloem points out the absence of studies that look ‘under the hood’, into the reduction of cells in the brain. He finds the studies he is familiar with worrying.

Becks: “For Parkinson’s you do indeed have to look at the decrease in black cells in the brain. There is currently no good protocol for this – and that will take some time.

“But there is some information available. It has not been proven that glyphosate cannot cause Parkinson’s, but it has also not been proven that it does cause Parkinson’s. Then it is ultimately up to politicians to weigh that: how do you deal with that as a society?”

Hempenius: “We look at brain damage in a broad sense, not at the underlying processes. We have a lot of data for glyphosate, from which we conclude that glyphosate is not neurotoxic. To remove doubts about Parkinson’s specifically, we really need to measure purely on Parkinson’s.”

How can we explain that a professor sometimes judges differently than the Ctgb?

Hempenius: “We look at the big picture: what happens when a laboratory animal is exposed through food or the skin. Take the microbiome in the intestines: if it is affected, it affects the absorption of nutrients and therefore the growth of animals. By taking measurements of the intestinal flora or the growth of a laboratory animal, you can already take into account underlying effects. Universities often look much more specifically at isolated organs, for example the microbiome within the intestines.”

Becks: “You could do experiments with intestinal cells in a petri dish in the laboratory. But the question is always: if a laboratory animal ingests glyphosate with food, does it end up in the intestinal flora? And in what dosage? You can look very specifically in a petri dish, but you also have a gastrointestinal tract and liver that influence the effects.”

A side effect of this is that academic studies appear much less often in the file than studies provided by the industry itself. Isn’t that undesirable?

Becks: “It is good to realize how exceptional it is that there are many public studies for glyphosate. It is already mandatory to include all relevant public literature in the assessment, but for many pesticides this is not or hardly the case. Then you actually only have the studies that are included in the requirements, which the industry itself must provide. There are controls to ensure its quality.

“But if society or politicians consider it undesirable for the industry to provide studies itself, this can be done differently. I can imagine that there is a discussion, but then politicians will have to adjust the system.”

What will the Ctgb do now with the knowledge gaps that still exist?

“If a knowledge gap is relevant to the use of a product containing glyphosate, it must be filled. The companies must convince us that there are no problems, for example by submitting a new study. If this is not possible, this will have consequences for admission. Then we could ban some uses of glyphosate.”

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